Need 2nd (psuedo) serial port

Need 2nd (psuedo) serial port

Post by John Murph » Mon, 06 Apr 1998 05:00:00

I've got a problem that I'm hoping someone can help me solve.

I have a toshiba C4400 laptop, which is kinda old.  It has a
serial port, and internal modem, a PS2 mouse port, printer
& vga connectors.  It also has a (damaged) docking station connector.

I had it in a docking station, but when the connector got
damaged, that all quit working.

I use the system to program a bunch of embedded systems.  I connect
to another linux embedded system using PPP over the serial port
for code updates / debugging. This works great.
   I also use the serial port to program the microcontrollers in
this system (aa bunch of 6811 devices).  The problems is that it's
a real pain to bring down ppp, switch cables, program the micro,
switch cables again, and bring ppp back up.  The code updates are
iteritive, so I'll end up doing this 15 times an hour.  I need a 2nd
serial port.  Of course, being a linux user, I'm hoping I can hack
a workaround.  I'm attached to this dumb laptop (It's got lots of duct
tape, etc.... It's a nice development system for this application
esp if I had another serial port.  What I'm hoping, in no particular
order, is that:
                1)  I can find the logic level send/rx lines
                    on the internal modem.  I opened things
                    & tried, but had no luck.
                2)  I can send/receive data via the PS2 mouse
                    port.  I don't know what level these operate
                    at, but if I can get data in and out serially, at
                    1200 or 9600 bps, I can build the shifters.
                3)  I can "bit bang" the parallel port pins and fake
                    a serial port in software.  My microcontroller
                    download app uses the /dev/ttyS* files and
                    the programming methods described in the linux
                    serial howto.

Any ideas on how I might get the functionality I need?  I don't want to
move to other hardware.  Also, in the event I do end up moving hardware,
after I get a working ppp link (ping, telnet, etc), whats the easiest
way to transfer 1 system (~150 MB) to the other?

Thanks for any help in advance.  I know this isn't the usual "I'm new
to linux and I need ppp" etc type of letter, so any help is greatly

John Murphy